A typical automatic analyzer involves the process of adding a reagent, which reacts with a particular substance to be analyzed, to a sample and stirring them. After a given amount of reaction time, a photometer is used, in the case of a biochemical analysis, to measure changes in the absorbance of the reacted liquid; in the case of an immunoassay or gene analysis, an actinometer such as photomultiplier tube and the like is used to count labeled substances that have bound to the substance to be analyzed. Examples of stirring methods include contact stirring, in which a paddle-like stirrer is immersed in a substance to be stirred and rotates or makes a reciprocal motion to stir the substance, and non-contact stirring, in which sound waves are radiated toward a substance to be stirred.
Patent Document 1 discloses a technique for enhancing stirring efficiency. Specifically, the rotational speed and stirring time of a stirrer and the insertion amount of a rotary stirrer with respect to a substance to be stirred are altered based on analysis conditions such as the kinds and amounts of reagent and dilution water and dilution rates. Patent Document 2 also discloses a technique for enabling effective stirring. This technique is based on the consideration of the top-surface heights of substances to be stirred when contained in different reaction vessels as well as their dynamical characteristics such as viscosity, density, and surface tension.